1. Field
The following description relates generally to wireless network communications, and more particularly to multiplexing demodulation reference signals in wireless communications.
2. Background
Wireless communication systems are widely deployed to provide various types of communication content such as, for example, voice, data, and so on. Typical wireless communication systems may be multiple-access systems capable of supporting communication with multiple users by sharing available system resources (e.g., bandwidth, transmit power, . . . ). Examples of such multiple-access systems may include code division multiple access (CDMA) systems, time division multiple access (TDMA) systems, frequency division multiple access (FDMA) systems, orthogonal frequency division multiple access (OFDMA) systems, and the like. Additionally, the systems can conform to specifications such as third generation partnership project (3GPP), 3GPP long term evolution (LTE), ultra mobile broadband (UMB), evolution data optimized (EV-DO), etc.
Generally, wireless multiple-access communication systems may simultaneously support communication for multiple mobile devices. Each mobile device may communicate with one or more base stations via transmissions on forward and reverse links. The forward link (or downlink) refers to the communication link from base stations to mobile devices, and the reverse link (or uplink) refers to the communication link from mobile devices to base stations. Further, communications between mobile devices and base stations may be established via single-input single-output (SISO) systems, multiple-input single-output (MISO) systems, multiple-input multiple-output (MIMO) systems, and so forth. In addition, mobile devices can communicate with other mobile devices (and/or base stations with other base stations) in peer-to-peer wireless network configurations.
In addition, a device can transmit demodulation reference signals (DM-RS) to the base station to enable channel estimation of communications received from the device. Moreover, for example, a device can communicate with the base station using single user (SU)-MIMO, which can be supported in LTE for example. In this example, the device can communicate with the base station over multiple layers in similar time/frequency resources. For example, signals can be transmitted by the device over multiple antennas over the same or similar time and frequency resources, such as one or more tones of one or more orthogonal frequency division multiplexing (OFDM) symbols, and received as a sum of the signals at the base station. Thus, for example, the device can transmit DM-RS to the base station for each of the signals to facilitate estimating channels over the same or similar time and frequency resources.